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6.9.3 X-RAID horizontal expansion-does it only work with same size now?
I've had these readyNAS running for about 8 years now. A year or two ago I moved them to 6.xxx.
I have 3x10TB disks and just inserted a 4TB that is going unused. I can format it, but it won't add it to the X-Raid volume. I've rebooted twice now. The 4TB drive is still gray next to the 3 blue disks. Nothing is happening. never had this happen before.
There is nothing in the logs other than the messages about added to head unit and disk has been formatted. I am running very low on space--but I would have expected a message saying, can't do this because...
I read threads that say you CAN'T put a smaller disk into the array. It has to be the same or bigger. Prior to 6.x mixing smaller or larger disks was inconsequential--XRaid2 added them in. It was brilliant and let me re-use older smaller drives. I swapped different size drives (any size) in more than a dozen times on each chassis and ReadyNAS just added it. Been bragging about how bulletproof these units have been for years.
However, I did realize that 6.x says XRAID... where 4.x called it X-RAID2.. Is there some gotcha here I'm not spotting?
Now... My 2nd ReadyNAS (same model, 6.9.2) started with 2x6TB + 2x4TB disks. I replaced a 6TB & a 4TB with two 10TB. So it is now 2x10Tb, 1x6TB, 1x4TB. After the multiple necessary reboots it expanded to 18.18TB (20TB per manufacturer's marketing). ALL GOOD.
Prior to 6.x mixing smaller or larger disks was inconsequential--XRaid2 added them in.
No, it didn't. 4.2.x firmware had the same restriction (plus a few more). It's actually fundamental to the way mdadm works.
For example, if you start with 4x4 TB, the system has a single RAID group of (also 4x4 TB RAID-5). If you add two 10 TB drives, that RAID group is enlarged to 6x4TB RAID-5 (20 TB). At this point you are only using 4 TB of the new drives. So the system creates a 2x6TB RAID-1 group that uses the rest of the space - and then concatenates both RAID groups into one 26 TB volume.
But if you start with 3x10 TB drives, the system would have a single 3x10 TB RAID-5 group. If you insert a 4 TB drive, the system would have split that RAID group into 2x4 TB RAID-5 + 3x6 TB RAID-5 in order to add it to the volume. It can't do that, so the new disk isn't added.
So ReadyNAS XRAID will add new RAID groups to handle newly inserted larger disks. But they won't split an existing RAID group - and that is what would be needed in order to handle insertion of a smaller disk.
Since whatever path you took before worked, you must not have ever added a disk that required the NAS to split an existing RAID group.
Now... My 2nd ReadyNAS (same model, 6.9.2) started with 2x6TB + 2x4TB disks. I replaced a 6TB & a 4TB with two 10TB. So it is now 2x10Tb, 1x6TB, 1x4TB.
That works fine, since the added disks are larger.
Initially you had two RAID groups: 4x4TB RAID-5 + 2x2TB RAID-1. After you upgraded you had 4x4 TB RAID-5 + 3x2TB RAID-5 + 2x4TB RAID-1. So this upgrade path didn't require splitting any RAID groups that were in the array.
However, I did realize that 6.x says XRAID... where 4.x called it X-RAID2..
That's just marketing. Originally the v1 sparc products had XRAID, but it didn't handle mixed drive sizes at all. When they introduced the 4.2.x systems they added support for mixed drive sizes, and rebranded it as XRAID2. When they introduced OS-6, they decided to drop the 2, and went back to the original XRAID branding.
Prior to 6.x mixing smaller or larger disks was inconsequential--XRaid2 added them in.
No, it didn't. 4.2.x firmware had the same restriction (plus a few more). It's actually fundamental to the way mdadm works.
For example, if you start with 4x4 TB, the system has a single RAID group of (also 4x4 TB RAID-5). If you add two 10 TB drives, that RAID group is enlarged to 6x4TB RAID-5 (20 TB). At this point you are only using 4 TB of the new drives. So the system creates a 2x6TB RAID-1 group that uses the rest of the space - and then concatenates both RAID groups into one 26 TB volume.
But if you start with 3x10 TB drives, the system would have a single 3x10 TB RAID-5 group. If you insert a 4 TB drive, the system would have split that RAID group into 2x4 TB RAID-5 + 3x6 TB RAID-5 in order to add it to the volume. It can't do that, so the new disk isn't added.
So ReadyNAS XRAID will add new RAID groups to handle newly inserted larger disks. But they won't split an existing RAID group - and that is what would be needed in order to handle insertion of a smaller disk.
Since whatever path you took before worked, you must not have ever added a disk that required the NAS to split an existing RAID group.
Now... My 2nd ReadyNAS (same model, 6.9.2) started with 2x6TB + 2x4TB disks. I replaced a 6TB & a 4TB with two 10TB. So it is now 2x10Tb, 1x6TB, 1x4TB.
That works fine, since the added disks are larger.
Initially you had two RAID groups: 4x4TB RAID-5 + 2x2TB RAID-1. After you upgraded you had 4x4 TB RAID-5 + 3x2TB RAID-5 + 2x4TB RAID-1. So this upgrade path didn't require splitting any RAID groups that were in the array.
However, I did realize that 6.x says XRAID... where 4.x called it X-RAID2..
That's just marketing. Originally the v1 sparc products had XRAID, but it didn't handle mixed drive sizes at all. When they introduced the 4.2.x systems they added support for mixed drive sizes, and rebranded it as XRAID2. When they introduced OS-6, they decided to drop the 2, and went back to the original XRAID branding.
Re: 6.9.3 X-RAID horizontal expansion-does it only work with same size now?
Thank you. That makes sense. I had a feeling it had to do with the 3x10 starting configuration, but couldn't see the mechanics behind it. Shame the log has nothing in it to indicate that it can't be added. Now I wish I had the foresight to start the unit with 2x10 a 6 and a 4 so I could make future use of smaller drives.
I have cycled about 18 disks through these two 4-drive chassis. One usually inheriting smaller drives pulled from the main one. While the main one probably always had same or bigger drives going in, the backup unit was a changimng mish-mosh of 2,3, and 4 for many years. They were never all matched, but the combos must have created several stripes that allowed me to freely mix 2,3 & ,4.
